It is known in the cathode fabrication art that Al.sub.2 O.sub.3 and WO.sub.3 react in a 1:3 molar ratio to form Al.sub.2 (WO.sub.4).sub.3 at temperatures greater than 900.degree. C. It is also known in the cathode fabrication art that the presence of Al.sub.2 (WO.sub.4).sub.3 can be detected in a tungsten billet that has been impregnated with the well known impregnant, Ba.sub.3 Al.sub.2 O.sub.6. The Al.sub.2 (WO.sub.4).sub.3 and the impregnant Ba.sub.3 Al.sub.2 O.sub.6 however react with each other to form BaAl.sub.2 O.sub.4 and BaWO.sub.4 without the formation of free barium metal. This is significant since it is the free barium metal that is responsible for electron emission in the aforementioned impregnated cathode. It is believed that the formation of Al.sub.2 (WO.sub.4).sub.3 acts as a deterrent to barium metal formation, and that electron emission is reduced. This occurs in conventional cathodes such as a porous billet of tungsten impregnated with Ba.sub.3 Al.sub.2 O.sub.6.